update: Started again this morning no faults revved to 5-6000 no issue, ran for about 10 mins, I shut it down. Went inside to have a bite and then come back out to start it and the problem re-appears. Seems something gets heat soaked and it struggles to get to 1750 rpm from idle, then as it approaqches 1750rpm, it will clean right up and rev no problem. During the stumbling, the afr gets really lean basically offscale. If it was a vacuum leak would the engine rpm be higher? I see no decrease of vacuum on my aem boost gauge, it sits at a steady 20in/hg.